As a conventional technique, a torque sensor for detecting a torque applied to a steering shaft by using a magnet and a magnetic sensor has been proposed (for example, refer to Patent Literature 1).
The torque sensor disclosed in Patent Literature 1 is provided at a connecting portion between a steering shaft connected with a steering wheel operated by a driver and a column shaft connected with the steering shaft through a torsion bar, and includes a cylindrical multipolar magnet connected to a steering shaft, a pair of magnetic yokes disposed within the magnetic field of the multipolar magnet and integrally rotated with the column shaft, a pair of magnetism collecting elements magnetically coupled to the pair of magnetic yokes, and a Hall IC for detecting a magnetic flux density, and the torque sensor detects a torque applied to the steering shaft by means of arrangement of a Hall IC between protrusions provided in each of the pair of magnetism collecting elements and detection of the magnetic flux density between the pair of magnetic yokes, by using the fact that when the torsion bar is twisted and deformed according to the torque applied to the steering shaft, the relative position between the multipolar magnet and the pair of magnetic yokes changes so that the magnetic flux density generated between the pair of magnetic yokes changes. Information on the detected torque is sent to an electric control unit (ECU), and the ECU sends a signal for controlling the assisting force applied to the column shaft to an assist mechanism that is connected to the column shaft and assists the driver's steering.
Here, as shown in FIGS. 18, 19(a) and 19(b), when the Hall IC 10w is mounted on a substrate (not shown) by the lead wire 11w, the minimum value of the distance Dw between the protrusions 13c and 14c provided on each of the pair of magnetism collecting elements is the thickness of the Hall IC 10w (for example, 1.5 mm). The Hall plate 100w of the Hall IC 10w is disposed between the protrusions 13c and 14c of the magnetism collecting elements so that the magnetic flux density between the pair of magnetic yokes can be detected more greatly and the distance Dw between the protrusions 13c and 14c of the magnetism collecting elements is made as small as possible so that magnetic flux density to be detected is maximized.
Further, as shown in FIG. 20 and FIGS. 21(a) and 21(b), there are cases where surface mounting of the Hall IC 10x on the substrate 11x is required when constructing the torque sensor. In this case, the minimum value of the distance Dx between the protrusions 13c and 14c provided on each of the pair of magnetism collecting elements becomes equal to the combined thickness of the thickness of the Hall IC 10x (for example, 1.5 mm) and the thickness of the substrate 11x (for example, 1.1 mm). Since the Hall plate 100x of the Hall IC 10x is disposed between the protrusions 13c and 14c of the magnetism collecting elements, the magnetic flux density between the pair of magnetic yokes is detected more greatly, but the distance Dx between the protrusions 13c and 14c of the magnetism collecting elements is increased by the thickness of the substrate 11x as compared with the distance Dw, and the magnetic flux density to be detected is reduced.
As a solution to the above problem, a torque sensor having a notch in a substrate has been proposed (for example, Patent Literatures 2, 3, and 4).
As shown in FIGS. 22, 23(a) and 23(b), the torque sensor disclosed in Patent Literatures 2, 3, and 4 is provided with a notch 110y on the substrate fly, and the protrusion 14c of the magnetism collecting element is arranged in the space formed by the notch 110y, whereby the minimum value of the distance Dy between the protrusions 13c and 14c of the magnetism collecting elements is set to the thickness of the Hall IC 10y (for example, 1.5 mm). The Hall plate 100y of the Hall IC 10y is disposed between the protrusions 13c and 14c of the magnetism collecting elements whose interval has been narrowed so that the magnetic flux density between the pair of magnetic yokes is detected more greatly and the distance Dy between protrusions 13c and 14c of the magnetism collecting elements is made substantially equal to the distance Dw, thereby maximizing the magnetic flux density to be detected.
As shown in FIGS. 24, 25(a) and 25(b), when the torque sensor is made, the Hall IC 10z is subjected to surface mounting on the substrate 11z, and in addition, a molding with a sealing material 12z is sometimes required.